Additive manufacturing of three-dimensional articles

ABSTRACT

The present invention relates to a method for prolonging lifetime of a triod electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: adjusting a cathode heating power at a predetermined value above a threshold heating value, which threshold heating value creates a predetermined X-ray signal emanating from the triod electron beam source, fusing the three-dimensional article with the electron beam source having the cathode heating power at a predetermined value above a threshold heating value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 62/256,525, filed Nov. 17, 2015; the contents of which as are hereby incorporated by reference in their entirety.

BACKGROUND

Technical Field

The present invention relates to a method for additive manufacturing of a three dimensional article by successively fusing individual layers of powder material.

Related Art

Freeform fabrication or additive manufacturing is a method for forming three-dimensional articles through successive fusion of chosen parts of powder layers applied to a worktable.

An additive manufacturing apparatus may comprise a work table on which the three-dimensional article is to be formed, a powder dispenser or powder distributor, arranged to lay down a thin layer of powder on the work table for the formation of a powder bed, a high energy beam for delivering energy to the powder whereby fusion of the powder takes place, elements for control of the energy given off by the energy beam over the powder bed for the formation of a cross section of the three-dimensional article through fusion of parts of the powder bed, and a controlling computer, in which information is stored concerning consecutive cross sections of the three-dimensional article. A three-dimensional article is formed through consecutive fusions of consecutively formed cross sections of powder layers, successively laid down by the powder dispenser.

In additive manufacturing a short manufacturing time and high quality of the finalized product is of outmost importance. What is also important is to reduce servicing of the additive manufacturing apparatus as much as possible. The life time of the cathode element is one thing which constantly requires service in form of exchange when being worn out. It is desirable to extend the lifetime of the cathode element. Today the electron beam source settings is mainly performed manually which may introduce settings which reduces the lifetime from the very outset and/or after a period of time when the performance of the cathode element has changed.

BRIEF SUMMARY

An object of various embodiments of the invention is to provide a method which prolongs the lifetime of an electron beam source in an additive manufacturing process. The above mentioned object is achieved by the features recited in the claims provided herein.

In a first aspect of various embodiments of the invention it is provided a method for prolonging lifetime of at least one electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: providing the at least one electron beam source emitting an electron beam for at least one of heating or fusing the powder material, where the electron beam source comprises a cathode, an anode, and a grid between the cathode and anode; setting an electron beam current, a cathode heating power, a grid potential Ug and a cathode potential Uc to predetermined start values, reducing the cathode heating power with a predetermined value and decreasing a Uc-Ug potential difference for maintaining the predetermined electron beam current, detecting an X-ray signals emanating from the electron beam source with at least one X-ray detector, repeating step c and d (the last two steps) until the detected X-ray signal is above a predetermined value, and increasing the cathode heating power by a predetermined safety value from a threshold heating power value which resulted in x-ray signals, emanating from the electron beam source, above the predetermined value.

An exemplary advantage of various embodiments of the present invention is that it gives much better control of the heating power of the cathode element than prior art technique. Another advantage is that it is possible to adjust the heating power depending on the actual hours the cathode element has been used. Yet another advantage of the present invention is that the heating power may be set optimally individually for different additive manufacturing machines.

In various example embodiments of the present invention steps c-d is performed during preheating of the surface prior to applying a new powder layer onto the surface, preheating of a new powder layer, powder distribution, post heat treatment of an already fused powder layer or during the fusion process. An exemplary advantage of at least these embodiments is that the method may be used at any given process step during additive manufacturing of the three dimensional article as well as prior to the manufacturing has started or after the manufacturing has been completed.

In various example embodiments of the present invention the start value of the electron beam current is between 20-50 mA. An exemplary advantage of at least these embodiments is that the method works for any suitable electron beam current which may be sued during additive manufacturing.

In various example embodiments of the present invention an updating of the heating power is performed between a fusion process of each layer. An exemplary advantage of at least these embodiments is that the heating power of the cathode element is constantly monitored and set for prolonging its lifetime.

In various example embodiments of the present invention further comprising the step of arranging the X-ray detector in the electron beam source. An exemplary advantage of at least these embodiments is that the detector is arranged for receiving x-rays emanating from the electron beam source only. In case of any background x-ray signal emanating from any other place in the additive manufacturing machine such X-rays may be filtered away easily.

In various example embodiments of the present invention further comprising the step of arranging the at least one x-ray detector out of sight from x-ray signals emanating from the powder layer. An exemplary advantage of at least these embodiments is that only X-rays emanating from the electron beam source is received and thereby eliminates any filtering or removal of background x-ray signals emanating from the powder surface for instance.

In another aspect of various embodiments of the present invention it is provided a method for prolonging lifetime of a triod electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: adjusting a cathode heating power at a predetermined value above a threshold heating value, which threshold heating value creates a predetermined X-ray signal emanating from the triod electron beam source, and fusing the three-dimensional article with the electron beam source having the cathode heating power at a predetermined value above a threshold heating value.

An exemplary advantage of at least this embodiment is that manufacturing of the three dimensional article is using a heating power of the cathode element which prolong the life time of the cathode element as much as possible. The predetermined value may be set individually based on the safety factor used.

In another aspect of various embodiments of the present invention it is provided a use of an X-ray detector for detecting x-rays emanating from an electron beam source in an apparatus for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together with the electron beam source so as to form the article.

In another aspect of various embodiments of the present invention it is provided a program element configured and arranged when executed on a computer a method for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: providing at least one electron beam source emitting an electron beam for heating and/or fusing the powder material, where the electron beam source comprising a cathode, an anode, and a grid between the cathode and anode, controlling the electron beam source in a first mode when the formation of the three dimensional article is in a first process step, controlling the electron beam source in a second mode when the formation of the three dimensional article is in a second process step, wherein an electron beam current from the electron beam source is controlled in a feed-forward mode in the first mode and the electron beam current is controlled in a feed-back mode in the second mode.

In still another aspect of various embodiments of the present invention it is provided a computer readable medium having stored thereon the program element.

In yet another aspect of various embodiments of the present invention it is provided a non-transitory computer program product comprising at least one non-transitory computer-readable storage medium having computer-readable program code portions embodied therein. In these embodiments, the computer-readable program code portions comprises: an executable portion configured for controlling an electron beam source in a first mode when formation of a three dimensional article is in a first process step, the electron beam source emitting an electron beam for at least one of heating or fusing individual layers of a powder material together so as to form the three-dimensional article, the electron beam source comprising a cathode, an anode, and a grid between the cathode and anode; and an executable portion configured for controlling the electron beam source in a second mode when the formation of the three dimensional article is in a second process step, wherein an electron beam current from the electron beam source is controlled in a feed-forward mode in the first mode and the electron beam current is controlled in a feed-back mode in the second mode. One executable portion may be utilized for all of these steps in certain embodiments.

All examples and exemplary embodiments described herein are non-limiting in nature and thus should not be construed as limiting the scope of the invention described herein. Still further, the advantages described herein, even where identified with respect to a particular exemplary embodiment, should not be necessarily construed in such a limiting fashion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The invention will be further described in the following, in a non-limiting way with reference to the accompanying drawings. Same characters of reference are employed to indicate corresponding similar parts throughout the several figures of the drawings:

FIG. 1 depicts, in a schematic view, an example embodiment of an electron beam source in which the inventive method may be implemented;

FIG. 2 depicts, in a schematic view, an example embodiment of an apparatus for producing a three dimensional product which may have an electron beam source according to FIG. 1;

FIG. 3 depicts the Cathode potential—grid potential as a function of electron beam current for different emissivity of a filament in an electron beam source;

FIG. 4 is a block diagram of an exemplary system 1020 according to various embodiments;

FIG. 5A is a schematic block diagram of a server 1200 according to various embodiments; and

FIG. 5B is a schematic block diagram of an exemplary mobile device 1300 according to various embodiments.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Various embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, embodiments of the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly known and understood by one of ordinary skill in the art to which the invention relates. The term “or” is used herein in both the alternative and conjunctive sense, unless otherwise indicated. Like numbers refer to like elements throughout.

Still further, to facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

The term “three-dimensional structures” and the like as used herein refer generally to intended or actually fabricated three-dimensional configurations (e.g., of structural material or materials) that are intended to be used for a particular purpose. Such structures, etc. may, for example, be designed with the aid of a three-dimensional CAD system.

The term “electron beam” as used herein in various embodiments refers to any charged particle beam. The sources of charged particle beam can include an electron gun, a linear accelerator and so on.

FIG. 2 depicts an embodiment of a freeform fabrication or additive manufacturing apparatus 21 in which the inventive method according to the present invention may be implemented.

The apparatus 21 comprising an electron beam gun 6; deflection coils 7; two powder hoppers 4, 14; a build platform 2; a build tank 10; a powder distributor 28; a powder bed 5; and a vacuum chamber 20.

The vacuum chamber 20 is capable of maintaining a vacuum environment via a vacuum system, which system may comprise a turbo molecular pump, a scroll pump, an ion pump and one or more valves which are well known to a skilled person in the art and therefore need no further explanation in this context. The vacuum system is controlled by a control unit 8.

The electron beam gun 6 is generating an electron beam which is used for pre heating of the powder, melting or fusing together powder material provided on the build platform 2 or post heat treatment of the already fused powder material. At least a portion of the electron beam gun 6 may be provided in the vacuum chamber 20. The control unit 8 may be used for controlling and managing the electron beam emitted from the electron beam gun 6. At least one focusing coil (not shown), at least one deflection coil 7, an optional coil for astigmatic correction (not shown) and an electron beam power supply (not shown) may be electrically connected to the control unit 8. In an example embodiment of the invention the electron beam gun 6 may generate a focusable electron beam with an accelerating voltage of about 15-60 kV and with a beam power in the range of 3-10 kW. The pressure in the vacuum chamber may be 10⁻³ mbar or lower when building the three-dimensional article by fusing the powder layer by layer with the energy beam.

The powder hoppers 4, 14 comprise the powder material to be provided on the build platform 2 in the build tank 10. The powder material may for instance be pure metals or metal alloys such as titanium, titanium alloys, aluminum, aluminum alloys, stainless steel, Co—Cr alloys, nickel based super alloys, etc.

The powder distributor 28 is arranged to lay down a thin layer of the powder material on the build platform 2. During a work cycle the build platform 2 will be lowered successively in relation to a fixed point in the vacuum chamber. In order to make this movement possible, the build platform 2 is in one embodiment of the invention arranged movably in vertical direction, i.e., in the direction indicated by arrow P. This means that the build platform 2 starts in an initial position, in which a first powder material layer of necessary thickness has been laid down. Means for lowering the build platform 2 may for instance be through a servo engine equipped with a gear, adjusting screws, etc. The servo engine may be connected to the control unit 8.

An electron beam may be directed over the build platform 2 causing the first powder layer to fuse in selected locations to form a first cross section of the three-dimensional article 3. The beam is directed over the build platform 2 from instructions given by the control unit 8. In the control unit 8 instructions for how to control the electron beam for each layer of the three-dimensional article is stored. The first layer of the three dimensional article 3 may be built on the build platform 2, which may be removable, in the powder bed 5 or on an optional start plate 16. The start plate 16 may be arranged directly on the build platform 2 or on top of a powder bed 5 which is provided on the build platform 2.

After a first layer is finished, i.e., the fusion of powder material for making a first layer of the three-dimensional article, a second powder layer is provided on the build platform 2. The thickness of the second layer may be determined by the distance the build platform is lowered in relation to the position where the first layer was built. The second powder layer is in various embodiments distributed according to the same manner as the previous layer. However, there might be alternative methods in the same additive manufacturing machine for distributing powder onto the work table. For instance, a first layer may be provided via a first powder distributor 28, a second layer may be provided by another powder distributor. The design of the powder distributor is automatically changed according to instructions from the control unit 8. A powder distributor 28 in the form of a single rake system, i.e., where one rake is catching powder fallen down from both a left powder hopper 4 and a right powder hopper 14, the rake as such can change design.

After having distributed the second powder layer on the build platform, the energy beam is directed over the work table causing the second powder layer to fuse in selected locations to form a second cross section of the three-dimensional article. Fused portions in the second layer may be bonded to fused portions of the first layer. The fused portions in the first and second layer may be melted together by melting not only the powder in the uppermost layer but also remelting at least a fraction of a thickness of a layer directly below the uppermost layer.

Sometimes it may be necessary to consider the charge distribution that is created in the powder as the electrons hit the powder bed 5. The charge distribution density depends on the following parameters: beam current, electron velocity (which is given by the accelerating voltage), beam scanning velocity, powder material and electrical conductivity of the powder, i.e., mainly the electrical conductivity between the powder grains. The latter is in turn a function of several parameters, such as the non-limiting examples of temperature, degree of sintering and powder grain size/size distribution.

Thus, for a given powder, i.e., a powder of a certain material with a certain grain size distribution, and a given accelerating voltage, it is possible, by varying the beam current (and thus the beam power) and the beam scanning velocity, to affect the charge distribution.

By varying these parameters in a controlled way, the electrical conductivity of the powder can gradually be increased by increasing the temperature of the powder. A powder that has a high temperature obtains a considerably higher conductivity which results in a lower density of the charge distribution since the charges quickly can diffuse over a large region. This effect is enhanced if the powder is allowed to be slightly sintered during a preheating process. When the conductivity has become sufficiently high, the powder can be fused together, i.e., melted or fully sintered, with predetermined values of the beam current and beam scanning velocity.

FIG. 1 depicts, in a schematic view, an exemplary embodiment of an electron beam source in which the inventive method may be implemented. The electron beam source 100 comprises a cathode 102, a grid 104 and an anode 106. Electrons emitted at the cathode 102 being on negative potential are accelerated towards the anode 106 and finally a target surface 118. A grid 104 is set at a predetermined distance from the cathode 102. The cathode 102 may be provided with a heating power which may cause the cathode to heat up, where upon the cathode 102 releases electrons by thermionic emission. The heating power is typically around 5 W for a lanthanum hexaboride (LaB6) cathode element.

An accelerator voltage 160 is provided between the cathode and the anode 106. The accelerator voltage 160 causes the emitted electrons from the cathode 102 to accelerate towards the anode 106 thus establishing an electron beam 120. The electron beam 120 may impinge on a substrate surface 118, which may be a powder layer in an additive manufacturing process. In order to guide and focus the electron beam there may further be arranged at least one focusing coil and at least one deflection coil.

In the electron beam source 100 the grid 104 is provided between the cathode 102 and the anode 106. The grid 104 may be arranged as a plate having an aperture. The aperture may be aligned with the cathode 102. The size of the aperture in the grid 104 may correspond to a cross section of the electron beam 120 at the position of the grid 104.

A grid voltage 180 may be provided between the grid 104 and the cathode 102 and may be adjusted between a negative blocking voltage and a full power voltage and thereby adjusting an electron beam current between 0—maximum electron beam current. In FIG. 1 the cathode 102 may be provided with a negative potential Uc of −20 kV to −100 kV. A first connection point 110 of the accelerator voltage 160 and a first connection point 114 of the grid voltage 180 may be fixed to the same potential of −20 kV to −100 kV. A second connection point 108 of the accelerator voltage 160 may be provided with ground potential. A second connection point 112 of the grid voltage 180 may be varied between the negative blocking voltage and the full power voltage. A second control unit 150 may be controlling the negative potential Ug on the second connection point 112 of the grid voltage in order to adjust the electron beam current to a desired value. The second control unit 150 may be a physically separate control unit in connection with the control unit 8 or fully integrated in the control unit 8.

The target surface 118 may be set to ground potential or a positive potential. The electron beam source 100 may also comprise means 170 for detecting the actual electron beam current. An example means for detecting the electron beam current on the target surface may be to detect the actual loading of the high voltage source providing the accelerator voltage 160, indicated by box 170 in FIG. 1. This may be done by simply measuring the electron beam passing between the first and second connection points 110 and 108 respectively. If the cathode is provided with a fixed negative voltage of −60 kV the negative blocking voltage may be around −61 kV, i.e., the second connection point 112 of the grid voltage is set at −61 kV and the first connection point 114 is set to −60 kV, for blocking the electrons by the grid 104. If starting to decrease the negative blocking voltage at the second connection point 112, some of the electrons emitted from the cathode will be allowed to pass the grid 104. By varying the grid voltage in this example embodiment between −61 kV to ˜−60 kV, when the cathode is provided with a fixed negative potential of −60 kV, the electron beam current may vary from 0 mA-maximum electron beam current which may be 25 mA for a predetermined size and shape of the cathode and a predetermined size and shape of the aperture in the grid 104. Other accelerator voltages and/or other size, shape and emissivity of the cathode and/or other size and shape of the aperture in the grid may affect the maximum electron beam current to be higher or lower than the exemplified 25 mA.

FIG. 3 depicts the cathode potential−grid potential as a function of electron beam current for different emissivity of a filament. When the grid voltage 180 is at a sufficiently high negative potential, i.e., the potential on connection point 112 is provided with a sufficient negative potential (negative blocking potential) compared to the negative potential on connection point 114, the electrons emanating from the cathode 102 will be blocked (repelled) by the negative potential on the grid 104 resulting in no electrons passing through the aperture in the grid 104. In such a case we are at the leftmost position in the graph in FIG. 3, i.e., zero electron beam current. As the potential difference between the cathode 102 and grid 104 is decreasing the electron beam current is increasing, i.e., we are moving to the right in the graph in FIG. 3. Uc represents the cathode potential and UG represents the grid potential.

A cathode 102 at different temperatures may emanate different amounts of electrons. In FIG. 3 it is illustrated 4 different graphs 310, 320, 330 and 340. A first graph 310 may represent a cathode at a first temperature. A second graph 320 may represent a cathode at a second temperature. A third graph 330 may represent a cathode at a third temperature. A fourth graph 310 may represent a cathode at a fourth temperature. The first temperature<the second temperature<the third temperature<the fourth temperature. Notably the temperature of the cathode may not be the only parameter that affects the numbers of emanating electrons. When the cathode is used its emissivity of electron may change in a similar manner as depicted in FIG. 3. An unused cathode may be represented by graph 340. The more the cathode 102 is used the last portion of the graph is shifted to the left. A combination of a change in temperature of the cathode and the degree of use may also be represented by the different graphs in FIG. 3, i.e., for relatively cold cathodes and well used the last portion will be shifted to the left and for a relatively hot and new cathode the graph will be shifted to the right.

The graph in FIG. 3 may be defined by applying a predetermined number of different Uc-Ug potentials and measuring the resulting electron beam current for the Uc-Ug potentials. The graph may be approximated by a mathematical expression, for instance a polynomial which is fitted to the graph.

The invention is how to prolong the life time of the cathode element. If providing an excessive amount of heating power the lifetime of the cathode element is heavily reduced. The invention is about how to determine the lowest acceptable heating power of the cathode element without affecting the electron beam current range of the electron beam source. If looking at FIG. 3, one needs to determine when the Uc-Ug starts to change abruptly for a specific electron beam current denoted by 310′, 320′, 330′. Since x-rays are created instantly as the electron beam hits the internal structure of the electron beam source it is a very good measure of an electron beam path within the electron beam source which is not correct. A very small amount of the electron beam is needed for creating a detectable X-ray signal.

For purposes of clarity, it is noted that the internal structure of the electron beam source, as reference above and herein-throughout may be a grid plate, an electron tube arranged as a last/final component in the electron beam source, or any component in the electron beam source.

The idea is to use an X-ray detector 190 provided in the electron beam source for detecting X-rays emanating from the electron beam source. Obviously x-rays are created when the electron beam is hitting the substrate 118 but the X-ray detector is out of sight from the x-rays and/or the x-rays emanating from the substrate will only create a background X-ray noise which is known and can be eliminated from the detected x-ray signal in detector 190.

In a first step the electron beam source is set to a predetermined electron beam current using a predetermined cathode hating power together with a predetermined grid potential Ug and a predetermined cathode potential Uc. The cathode potential may be kept constant throughout the determination of the heating power of the cathode element. An X-ray signal is detected by the X-ray detector 190. If the X-ray signal is below a predetermined value the cathode heating power may be reduced by a predetermined heating power step. In order to keep the electron beam current constant when the heating power is reduced the Uc-Ug potential needs to be decreased. The heating power step may for instance be 0.05 W. The X-ray detector is again detecting the X-ray signal. If the X-ray signal is still below the predetermined value a further decrease in heating power is performed together with a new decrease in Uc-Ug potential and yet a new X-ray measurement is made. However, if the X-ray signal is above a predetermined value, it means that the heating power is too low for creating a predetermined electron beam current. As the heating power is reduced the Uc-Ug potential is also reduced in order to maintain the constant electron beam current. At a certain point the Uc-Ug potential will be so low that electron emissions from the cathode element will hit internal elements within the electron beam source and thereby create X-ray emission. A relatively low grid potential from a relatively “cold” cathode element will result in electron emission in direction not only towards the substrate but also electron emission which will hit internal elements within the electron beam source.

X-rays detected by the detector 190 are mainly emanating from the electron beam source as such. This means that when the electron beam hits the internal structure of the electron beam source before the electron beam is leaving the electron beam source. One or a plurality of detectors may be used. A detector may be arranged for receiving x-rays signals from a particular area of the electron beam source. If the complete electron beam source is to be detected more than one x-ray detector may be needed.

The risk of hitting the internal structure with the complete electron beam is reduced and/or eliminated if the starting value of the heating power is chosen in a safe interval where one knows by experience that no x-rays should be detected. In the exemplified embodiment a Uc-Ug of about 300 V or higher and a heating power above 5 w may be a good starting point for a lanthanum hexaboride cathode element. If the heating power is reduced by predetermined steps closely enough spaced apart the method will prohibit full impact of the electron beam into the internal structure of the electron beam source. This may reduce the contamination of cathode element and thereby further increase its lifetime.

The constant electron beam current used may be the maximum current to be used in the additive manufacturing process. If the heating power is determined not to create x-ray emissions above a predetermined level for the maximum electron beam current, then electron beam currents lower than the maximum electron beam current will also not create X-ray emission above the level.

A predetermined safety value is added to a threshold heating power, which threshold heating power resulted in the X-ray signal above the predetermined value.

The X-ray measurement may be done prior to starting to additively manufacture a three dimensional article. The x-ray measurement may also be made during preheating powder material during a build or post heat treatment of already fused material during a build. In another example embodiment the X-ray measurement is made during powder distribution. The x-ray emanating from the electron beam source may also be detected during the fusion process.

A usable range of heating powers of a cathode element of the electron beam source may be defined as follows. A lowest value in the range may be the heating power of the cathode element for a given electron beam current which creates an X-ray signal from the electron beam source which is lower than a predetermined value. The predetermined value may be 0.0001 mSv. The upper limit may be chosen arbitrary. However, the higher the heating power above the lowest value the shorter the life time of the cathode element.

A sign of a worn out cathode element may be a too large deviation from the previous cathode heating power setting. This may be used as a warning for the operator of the additive manufacturing machine that the cathode element needs to be replaced if the heating power is increased above a predetermined percentage of the previous heating power setting. In an example embodiment a maximum value in which the heating power may be increased from the previous setting without having to be replaced may be 0.3 W.

In an arrangement where the electron beam is bent in order to impinge perpendicular onto the substrate, i.e., in a case where the electron beams emanating from the electron beam source is travelling in a direction at an angle different to 90 degrees from a substrate surface 118. X-rays emanating from the electron beam source including electron beam bending coils, may be a measure of good or bad electron beam path. An X-ray signal may be a sign of an electron beam hitting the internal structure of the electron beam source before it is leaving the electron beam source.

The start value of the electron beam current may be 20-50 mA.

An updating of the heating power may be performed regularly during the manufacturing of the three-dimensional article. In an example embodiment the updating of the heating power may be performed in regular time intervals of for instance 5 minutes. In an alternative embodiment the updating is performed only during specific process steps such as powder distribution, preheating of powder material in order to reach a predetermined temperature interval or post heat treatment of already fused powder material in order to maintain the temperature of the three-dimensional article within a predetermined temperature interval.

The heating power is in an example embodiment reduced in steps of 0.05 W. A larger step may introduce a risk of hitting the internal structure with a too large amount of the electron beam which may cause unwanted contamination and reduced lifetime of the cathode element. A too small step may require too much time before knowing which heating power to use.

In an example embodiment a triod electron beam source may be used for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article. The triod electron beam source comprises an anode, a cathode and a grid. A cathode heating power is kept at a predetermined value above a threshold heating value which threshold heating value creates a predetermined X-ray signal emanating from the triod electron beam source. The three dimensional article may be fused using the cathode heating power kept at the predetermined value above the threshold heating value.

In another aspect of the invention it is provided a program element configured and arranged when executed on a computer to implement a method for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: providing at least one electron beam source emitting an electron beam for heating and/or fusing the powder material, where the electron beam source comprising a cathode, an anode, and a grid between the cathode and anode, controlling the electron beam source in a first mode when the formation of the three dimensional article is in a first process step, controlling the electron beam source in a second mode when the formation of the three dimensional article is in a second process step, wherein an electron beam current from the electron beam source is controlled in a feed-forward mode in the first mode and the electron beam current is controlled in a feed-back mode in the second mode. The program may be installed in a computer readable storage medium. The computer readable storage medium may be the control unit 8, the control unit 150, or another separate and distinct control unit. The computer readable storage medium and the program element, which may comprise computer-readable program code portions embodied therein, may further be contained within a non-transitory computer program product. Further details regarding these features and configurations are provided, in turn, below.

As mentioned, various embodiments of the present invention may be implemented in various ways, including as non-transitory computer program products. A computer program product may include a non-transitory computer-readable storage medium storing applications, programs, program modules, scripts, source code, program code, object code, byte code, compiled code, interpreted code, machine code, executable instructions, and/or the like (also referred to herein as executable instructions, instructions for execution, program code, and/or similar terms used herein interchangeably). Such non-transitory computer-readable storage media include all computer-readable media (including volatile and non-volatile media).

In one embodiment, a non-volatile computer-readable storage medium may include a floppy disk, flexible disk, hard disk, solid-state storage (SSS) (e.g., a solid state drive (SSD), solid state card (SSC), solid state module (SSM)), enterprise flash drive, magnetic tape, or any other non-transitory magnetic medium, and/or the like. A non-volatile computer-readable storage medium may also include a punch card, paper tape, optical mark sheet (or any other physical medium with patterns of holes or other optically recognizable indicia), compact disc read only memory (CD-ROM), compact disc compact disc-rewritable (CD-RW), digital versatile disc (DVD), Blu-ray disc (BD), any other non-transitory optical medium, and/or the like. Such a non-volatile computer-readable storage medium may also include read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory (e.g., Serial, NAND, NOR, and/or the like), multimedia memory cards (MMC), secure digital (SD) memory cards, SmartMedia cards, CompactFlash (CF) cards, Memory Sticks, and/or the like. Further, a non-volatile computer-readable storage medium may also include conductive-bridging random access memory (CBRAM), phase-change random access memory (PRAM), ferroelectric random-access memory (FeRAM), non-volatile random-access memory (NVRAM), magnetoresistive random-access memory (MRAM), resistive random-access memory (RRAM), Silicon-Oxide-Nitride-Oxide-Silicon memory (SONOS), floating junction gate random access memory (FJG RAM), Millipede memory, racetrack memory, and/or the like.

In one embodiment, a volatile computer-readable storage medium may include random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), fast page mode dynamic random access memory (FPM DRAM), extended data-out dynamic random access memory (EDO DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), double data rate type two synchronous dynamic random access memory (DDR2 SDRAM), double data rate type three synchronous dynamic random access memory (DDR3 SDRAM), Rambus dynamic random access memory (RDRAM), Twin Transistor RAM (TTRAM), Thyristor RAM (T-RAM), Zero-capacitor (Z-RAM), Rambus in-line memory module (RIMM), dual in-line memory module (DIMM), single in-line memory module (SIMM), video random access memory VRAM, cache memory (including various levels), flash memory, register memory, and/or the like. It will be appreciated that where embodiments are described to use a computer-readable storage medium, other types of computer-readable storage media may be substituted for or used in addition to the computer-readable storage media described above.

As should be appreciated, various embodiments of the present invention may also be implemented as methods, apparatus, systems, computing devices, computing entities, and/or the like, as have been described elsewhere herein. As such, embodiments of the present invention may take the form of an apparatus, system, computing device, computing entity, and/or the like executing instructions stored on a computer-readable storage medium to perform certain steps or operations. However, embodiments of the present invention may also take the form of an entirely hardware embodiment performing certain steps or operations.

Various embodiments are described below with reference to block diagrams and flowchart illustrations of apparatuses, methods, systems, and computer program products. Thus, it should be understood that each block of the block diagrams and flowchart illustrations may be implemented in the form of a computer program product, an entirely hardware embodiment, a combination of hardware and computer program products, and/or apparatus, systems, computing devices, computing entities, and/or the like carrying out instructions, operations, steps, and similar words used interchangeably (e.g., the executable instructions, instructions for execution, program code, and/or the like) on a computer-readable storage medium for execution. For example, retrieval, loading, and execution of code may be performed sequentially such that one instruction is retrieved, loaded, and executed at a time. In some exemplary embodiments, retrieval, loading, and/or execution may be performed in parallel such that multiple instructions are retrieved, loaded, and/or executed together. Thus, such embodiments can produce specifically-configured machines performing the steps or operations specified in the block diagrams and flowchart illustrations. Accordingly, the block diagrams and flowchart illustrations support various combinations of embodiments for performing the specified instructions, operations, or steps.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including computer-readable instructions for implementing the functionality specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart block or blocks.

Accordingly, blocks of the block diagrams and flowchart illustrations support various combinations for performing the specified functions, combinations of operations for performing the specified functions and program instructions for performing the specified functions. It should also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, could be implemented by special purpose hardware-based computer systems that perform the specified functions or operations, or combinations of special purpose hardware and computer instructions.

FIG. 4 is a block diagram of an exemplary system 1020 that can be used in conjunction with various embodiments of the present invention. In at least the illustrated embodiment, the system 1020 may include one or more central computing devices 1110, one or more distributed computing devices 1120, and one or more distributed handheld or mobile devices 1300, all configured in communication with a central server 1200 (or control unit) via one or more networks 1130. While FIG. 4 illustrates the various system entities as separate, standalone entities, the various embodiments are not limited to this particular architecture.

According to various embodiments of the present invention, the one or more networks 1130 may be capable of supporting communication in accordance with any one or more of a number of second-generation (2G), 2.5G, third-generation (3G), and/or fourth-generation (4G) mobile communication protocols, or the like. More particularly, the one or more networks 1130 may be capable of supporting communication in accordance with 2G wireless communication protocols IS-136 (TDMA), GSM, and IS-95 (CDMA). Also, for example, the one or more networks 1130 may be capable of supporting communication in accordance with 2.5G wireless communication protocols GPRS, Enhanced Data GSM Environment (EDGE), or the like. In addition, for example, the one or more networks 1130 may be capable of supporting communication in accordance with 3G wireless communication protocols such as Universal Mobile Telephone System (UMTS) network employing Wideband Code Division Multiple Access (WCDMA) radio access technology. Some narrow-band AMPS (NAMPS), as well as TACS, network(s) may also benefit from embodiments of the present invention, as should dual or higher mode mobile stations (e.g., digital/analog or TDMA/CDMA/analog phones). As yet another example, each of the components of the system 5 may be configured to communicate with one another in accordance with techniques such as, for example, radio frequency (RF), Bluetooth™, infrared (IrDA), or any of a number of different wired or wireless networking techniques, including a wired or wireless Personal Area Network (“PAN”), Local Area Network (“LAN”), Metropolitan Area Network (“MAN”), Wide Area Network (“WAN”), or the like.

Although the device(s) 1110-1300 are illustrated in FIG. 4 as communicating with one another over the same network 1130, these devices may likewise communicate over multiple, separate networks.

According to one embodiment, in addition to receiving data from the server 1200, the distributed devices 1110, 1120, and/or 1300 may be further configured to collect and transmit data on their own. In various embodiments, the devices 1110, 1120, and/or 1300 may be capable of receiving data via one or more input units or devices, such as a keypad, touchpad, barcode scanner, radio frequency identification (RFID) reader, interface card (e.g., modem, etc.) or receiver. The devices 1110, 1120, and/or 1300 may further be capable of storing data to one or more volatile or non-volatile memory modules, and outputting the data via one or more output units or devices, for example, by displaying data to the user operating the device, or by transmitting data, for example over the one or more networks 1130.

In various embodiments, the server 1200 includes various systems for performing one or more functions in accordance with various embodiments of the present invention, including those more particularly shown and described herein. It should be understood, however, that the server 1200 might include a variety of alternative devices for performing one or more like functions, without departing from the spirit and scope of the present invention. For example, at least a portion of the server 1200, in certain embodiments, may be located on the distributed device(s) 1110, 1120, and/or the handheld or mobile device(s) 1300, as may be desirable for particular applications. As will be described in further detail below, in at least one embodiment, the handheld or mobile device(s) 1300 may contain one or more mobile applications 1330 which may be configured so as to provide a user interface for communication with the server 1200, all as will be likewise described in further detail below.

FIG. 5A is a schematic diagram of the server 1200 according to various embodiments. The server 1200 includes a processor 1230 that communicates with other elements within the server via a system interface or bus 1235. Also included in the server 1200 is a display/input device 1250 for receiving and displaying data. This display/input device 1250 may be, for example, a keyboard or pointing device that is used in combination with a monitor. The server 1200 further includes memory 1220, which preferably includes both read only memory (ROM) 1226 and random access memory (RAM) 1222. The server's ROM 1226 is used to store a basic input/output system 1224 (BIOS), containing the basic routines that help to transfer information between elements within the server 1200. Various ROM and RAM configurations have been previously described herein.

In addition, the server 1200 includes at least one storage device or program storage 210, such as a hard disk drive, a floppy disk drive, a CD Rom drive, or optical disk drive, for storing information on various computer-readable media, such as a hard disk, a removable magnetic disk, or a CD-ROM disk. As will be appreciated by one of ordinary skill in the art, each of these storage devices 1210 are connected to the system bus 1235 by an appropriate interface. The storage devices 1210 and their associated computer-readable media provide nonvolatile storage for a personal computer. As will be appreciated by one of ordinary skill in the art, the computer-readable media described above could be replaced by any other type of computer-readable media known in the art. Such media include, for example, magnetic cassettes, flash memory cards, digital video disks, and Bernoulli cartridges.

Although not shown, according to an embodiment, the storage device 1210 and/or memory of the server 1200 may further provide the functions of a data storage device, which may store historical and/or current delivery data and delivery conditions that may be accessed by the server 1200. In this regard, the storage device 1210 may comprise one or more databases. The term “database” refers to a structured collection of records or data that is stored in a computer system, such as via a relational database, hierarchical database, or network database and as such, should not be construed in a limiting fashion.

A number of program modules (e.g., exemplary modules 1400-1700) comprising, for example, one or more computer-readable program code portions executable by the processor 1230, may be stored by the various storage devices 1210 and within RAM 1222. Such program modules may also include an operating system 1280. In these and other embodiments, the various modules 1400, 1500, 1600, 1700 control certain aspects of the operation of the server 1200 with the assistance of the processor 1230 and operating system 1280. In still other embodiments, it should be understood that one or more additional and/or alternative modules may also be provided, without departing from the scope and nature of the present invention.

In various embodiments, the program modules 1400, 1500, 1600, 1700 are executed by the server 1200 and are configured to generate one or more graphical user interfaces, reports, instructions, and/or notifications/alerts, all accessible and/or transmittable to various users of the system 1020. In certain embodiments, the user interfaces, reports, instructions, and/or notifications/alerts may be accessible via one or more networks 1130, which may include the Internet or other feasible communications network, as previously discussed.

In various embodiments, it should also be understood that one or more of the modules 1400, 1500, 1600, 1700 may be alternatively and/or additionally (e.g., in duplicate) stored locally on one or more of the devices 1110, 1120, and/or 1300 and may be executed by one or more processors of the same. According to various embodiments, the modules 1400, 1500, 1600, 1700 may send data to, receive data from, and utilize data contained in one or more databases, which may be comprised of one or more separate, linked and/or networked databases.

Also located within the server 1200 is a network interface 1260 for interfacing and communicating with other elements of the one or more networks 1130. It will be appreciated by one of ordinary skill in the art that one or more of the server 1200 components may be located geographically remotely from other server components. Furthermore, one or more of the server 1200 components may be combined, and/or additional components performing functions described herein may also be included in the server.

While the foregoing describes a single processor 1230, as one of ordinary skill in the art will recognize, the server 1200 may comprise multiple processors operating in conjunction with one another to perform the functionality described herein. In addition to the memory 1220, the processor 1230 can also be connected to at least one interface or other means for displaying, transmitting and/or receiving data, content or the like. In this regard, the interface(s) can include at least one communication interface or other means for transmitting and/or receiving data, content or the like, as well as at least one user interface that can include a display and/or a user input interface, as will be described in further detail below. The user input interface, in turn, can comprise any of a number of devices allowing the entity to receive data from a user, such as a keypad, a touch display, a joystick or other input device.

As will be understood, the processing element 305 may be embodied in a number of different ways. For example, the processing element or processor may be embodied as one or more complex programmable logic devices (CPLDs), microprocessors, multi-core processors, coprocessing entities, application-specific instruction-set processors (ASIPs), and/or controllers. Further, the processing element may be embodied as one or more other processing devices or circuitry. The term circuitry may refer to an entirely hardware embodiment or a combination of hardware and computer program products. Thus, the processing element may be embodied as integrated circuits, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), hardware accelerators, other circuitry, and/or the like. As will therefore be understood, the processing element may be configured for a particular use or configured to execute instructions stored in volatile or non-volatile media or otherwise accessible to the processing element. As such, whether configured by hardware or computer program products, or by a combination thereof, the processing element may be capable of performing steps or operations according to embodiments of the present invention when configured accordingly.

Still further, while reference is made to the “server” 1200, as one of ordinary skill in the art will recognize, embodiments of the present invention are not limited to traditionally defined server architectures. Still further, the system of embodiments of the present invention is not limited to a single server, or similar network entity or mainframe computer system. Other similar architectures including one or more network entities operating in conjunction with one another to provide the functionality described herein may likewise be used without departing from the spirit and scope of embodiments of the present invention. For example, a mesh network of two or more personal computers (PCs), similar electronic devices, or handheld portable devices, collaborating with one another to provide the functionality described herein in association with the server 1200 may likewise be used without departing from the spirit and scope of embodiments of the present invention.

According to various embodiments, many individual steps of a process may or may not be carried out utilizing the computer systems and/or servers described herein, and the degree of computer implementation may vary, as may be desirable and/or beneficial for one or more particular applications.

FIG. 5B provides an illustrative schematic representative of a mobile device 1300 that can be used in conjunction with various embodiments of the present invention. Mobile devices 1300 can be operated by various parties. As shown in FIG. 5B, a mobile device 1300 may include an antenna 1312, a transmitter 1304 (e.g., radio), a receiver 1306 (e.g., radio), and a processing element 1308 that provides signals to and receives signals from the transmitter 1304 and receiver 1306, respectively.

The signals provided to and received from the transmitter 1304 and the receiver 1306, respectively, may include signaling data in accordance with an air interface standard of applicable wireless systems to communicate with various entities, such as the server 1200, the distributed devices 1110, 1120, and/or the like. In this regard, the mobile device 1300 may be capable of operating with one or more air interface standards, communication protocols, modulation types, and access types. More particularly, the mobile device 1300 may operate in accordance with any of a number of wireless communication standards and protocols. In a particular embodiment, the mobile device 1300 may operate in accordance with multiple wireless communication standards and protocols, such as GPRS, UMTS, CDMA2000, 1×RTT, WCDMA, TD-SCDMA, LTE, E-UTRAN, EVDO, HSPA, HSDPA, Wi-Fi, WiMAX, UWB, IR protocols, Bluetooth protocols, USB protocols, and/or any other wireless protocol.

Via these communication standards and protocols, the mobile device 1300 may according to various embodiments communicate with various other entities using concepts such as Unstructured Supplementary Service data (USSD), Short Message Service (SMS), Multimedia Messaging Service (MMS), Dual-Tone Multi-Frequency Signaling (DTMF), and/or Subscriber Identity Module Dialer (SIM dialer). The mobile device 1300 can also download changes, add-ons, and updates, for instance, to its firmware, software (e.g., including executable instructions, applications, program modules), and operating system.

According to one embodiment, the mobile device 1300 may include a location determining device and/or functionality. For example, the mobile device 1300 may include a GPS module adapted to acquire, for example, latitude, longitude, altitude, geocode, course, and/or speed data. In one embodiment, the GPS module acquires data, sometimes known as ephemeris data, by identifying the number of satellites in view and the relative positions of those satellites.

The mobile device 1300 may also comprise a user interface (that can include a display 1316 coupled to a processing element 1308) and/or a user input interface (coupled to a processing element 308). The user input interface can comprise any of a number of devices allowing the mobile device 1300 to receive data, such as a keypad 1318 (hard or soft), a touch display, voice or motion interfaces, or other input device. In embodiments including a keypad 1318, the keypad can include (or cause display of) the conventional numeric (0-9) and related keys (#, *), and other keys used for operating the mobile device 1300 and may include a full set of alphabetic keys or set of keys that may be activated to provide a full set of alphanumeric keys. In addition to providing input, the user input interface can be used, for example, to activate or deactivate certain functions, such as screen savers and/or sleep modes.

The mobile device 1300 can also include volatile storage or memory 1322 and/or non-volatile storage or memory 1324, which can be embedded and/or may be removable. For example, the non-volatile memory may be ROM, PROM, EPROM, EEPROM, flash memory, MMCs, SD memory cards, Memory Sticks, CBRAM, PRAM, FeRAM, RRAM, SONOS, racetrack memory, and/or the like. The volatile memory may be RAM, DRAM, SRAM, FPM DRAM, EDO DRAM, SDRAM, DDR SDRAM, DDR2 SDRAM, DDR3 SDRAM, RDRAM, RIMM, DIMM, SIMM, VRAM, cache memory, register memory, and/or the like. The volatile and non-volatile storage or memory can store databases, database instances, database mapping systems, data, applications, programs, program modules, scripts, source code, object code, byte code, compiled code, interpreted code, machine code, executable instructions, and/or the like to implement the functions of the mobile device 1300.

The mobile device 1300 may also include one or more of a camera 1326 and a mobile application 1330. The camera 1326 may be configured according to various embodiments as an additional and/or alternative data collection feature, whereby one or more items may be read, stored, and/or transmitted by the mobile device 1300 via the camera. The mobile application 1330 may further provide a feature via which various tasks may be performed with the mobile device 1300. Various configurations may be provided, as may be desirable for one or more users of the mobile device 1300 and the system 1020 as a whole.

It will be appreciated that many variations of the above systems and methods are possible, and that deviation from the above embodiments are possible, but yet within the scope of the claims. Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Such modifications may, for example, involve using a different source of energy beam than the exemplified electron beam such as a laser beam. Other materials than metallic powder may be used, such as the non-limiting examples of: electrically conductive polymers and powder of electrically conductive ceramics. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 

The invention claimed is:
 1. A method for prolonging lifetime of at least one electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: providing the at least one electron beam source emitting an electron beam for at least one of heating or fusing the powder material, wherein the electron beam source comprises a cathode, an anode, and a grid between the cathode and anode; setting an electron beam current, a cathode heating power, a grid potential (Ug) and a cathode potential (Uc) to predetermined start values; reducing the cathode heating power with a predetermined value and decreasing a Uc-Ug potential difference for maintaining the predetermined electron beam current; detecting an X-ray signals emanating from the electron beam source with at least one X-ray detector; repeating said reducing and detecting steps until the detected X-ray signal is above a predetermined value; and increasing the cathode heating power by a predetermined safety value from a threshold heating power value which resulted in x-ray signals, emanating from the electron beam source, above the predetermined value.
 2. The method according to claim 1, wherein said reducing and detecting steps are performed during preheating of the surface prior to applying a new powder layer onto the surface, preheating of a new powder layer, powder distribution, and post heat treatment of an already fused powder layer or during the fusion process.
 3. The method according to claim 1, wherein the start value of the electron beam current is between 20-50 mA.
 4. The method according to claim 1, wherein an updating of the cathode heating power is performed between a fusion process of each layer.
 5. The method according to claim 1, further comprising the step of arranging the X-ray detector in the electron beam source.
 6. The method according to claim 1, wherein the start value of the cathode heating power is about 5 W.
 7. The method according to claim 1, wherein the predetermined value in which the cathode heating power is reduced is in steps of 0.05 W.
 8. The method according to claim 1, wherein the predetermined safety value is between 0.4-0.8 W.
 9. The method according to claim 1, further comprising the step of filtering out any x-ray signal not emanating from the electron beam source.
 10. The method according to claim 1, further comprising the step of arranging the at least one x-ray detector out of sight from x-ray signals emanating from the powder layer.
 11. An apparatus for forming a three-dimensional article through successively depositing individual layers of powder material so as to form the article, the apparatus comprising: at least one electron beam source emitting an electron beam for at least one of heating or fusing the powder material, where the electron beam source comprises a cathode, an anode, and a grid between the cathode and anode; an X-ray detector for detecting x-rays emanating from the at least one electron beam source; and at least one control unit, the at least one control unit being configured for: setting an electron beam current, a cathode heating power, a grid potential (Ug) and a cathode potential (Uc) to predetermined start values, reducing the cathode heating power with a predetermined value and decreasing a Uc-Ug potential difference for maintaining the predetermined electron beam current, detecting, via the at least one X-ray detector, X-ray signals emanating from the electron beam source, repeating the reducing and detecting steps until the detected X-ray signal is above a predetermined value, and increasing the cathode heating power by a predetermined safety value from a threshold heating power value which resulted in x-ray signals, emanating from the electron beam source, above the predetermined value, so as to establish a usable range of heating powers of a cathode element of the electron beam source.
 12. The apparatus of claim 11, wherein the start value of the electron beam current is between 20-50 mA.
 13. The apparatus of claim 11, wherein the X-ray detector is positioned in the electron beam source.
 14. The apparatus of claim 11, wherein the X-ray detector is positioned out of sight from x-ray signals emanating from the powder layer.
 15. The apparatus of claim 11, wherein at least one of: the start value of the cathode heating power is about 5 W; the predetermined safety value is between 0.4-0.8 W; or the predetermined value in which the cathode heating power is reduced is in steps of 0.05 W.
 16. A computer program product comprising at least one non-transitory computer-readable storage medium having computer-readable program code portions embodied therein, the computer-readable program code portions comprising at least one executable portion configured for: setting an electron beam current, a cathode heating powder, a grid potential (Ug) and a cathode potential (Uc) to predetermined start values; reducing the cathode heating power with a predetermined value and decreasing a Uc-Ug potential difference for maintaining the predetermined electron beam current; detecting X-ray signal from the electron beam source with an X-ray detector; repeating the reducing and detecting step until the detected X-ray signal is above a predetermined value; and increasing the cathode heating power by a predetermined value from the value which resulted in x-ray signals above the predetermined value and using the electron beam for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article.
 17. The computer program product of claim 16, wherein the at least one executable portion is further configured for updating the cathode heating power between a fusion process of each layer.
 18. The computer program product of claim 16, wherein the at least one executable portion is further configured for filtering out any x-ray signal not emanating from the electron beam source.
 19. A method for prolonging lifetime of a triod electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: adjusting a cathode heating power with a control unit at a predetermined value above a threshold heating value, which threshold heating value creates a predetermined X-ray signal emanating from the triod electron beam source; and fusing the three-dimensional article with the electron beam source having the cathode heating power at a predetermined value above a threshold heating value. 